In the diagnosis of thyroid nodules and goiter, further data have been accumulated on the utility of fine needle aspiration cytology in preoperative diagnosis. This has also been an effective means of diagnosing lymphocytic thyroiditis. In the treatment of thyroid cancer, the serum thyroglobulin levels are being evaluated in correlation with the previously completed study of whole body 131I scanning. The method promises to be useful provided that patients are allowed to become at least mildly hypothyroid. In the treatment of hyperthyroidism, it was found that both iodide and lithium are effective in controlling hyperthyroidism after the use of relatively low dose 131I therapy. In the amounts used, iodide produced a greater response than lithium. In the syndrome of inappropriate secretion of thyrotropin (TSH), iodothyronine metabolism was studied in two patients. The metabolic clearance of T4 and T3 was low relative to their circulating hormone levels, but the conversion of T4 to T3 was not impaired. This suggests a possible defect in the entry of thyroid hormones into cells. In the syndrome of postpartum thyroiditis with transient hypothyroidism, several additional patients have been detected and studied.